Arrow functions

Like a closure, only slimmer

• Added in: PHP 7.4
• What it gives you: a compact syntax for short functions that automatically see variables from the surrounding scope and always return a result.

Things you need to know

• they always return a value;
• they can contain only a single expression — no {} and no multi-statement blocks;
• they automatically inherit variables from the surrounding scope, without use($x);
• they read as an expression, not as a statement.

Why it's convenient

• less boilerplate;
• expressiveness in callbacks (map, filter, reduce);
• better readability, especially in collections and streams;
• a fit for any place where you need a minimal handler.

Real-world examples

Transforming an array

$prices = [100, 200, 300];
$tax = 0.2;

// ❌ A regular anonymous function
$withTax = array_map(function (int $p) use ($tax) {
    return $p * (1 + $tax);
}, $prices);

// ✅ An arrow function
$withTax = array_map(fn(int $p) => $p * (1 + $tax), $prices);

Filtering elements

$activeUsers = array_filter($users, fn(User $u) => $u->active);

Computing a value

$total = array_reduce($orders, fn(int $sum, Order $o) => $sum + $o->amount, 0);

A simple calculator with access to an outer variable

$multiplier = 3;
$calc = fn(int $v) => $v * $multiplier;

echo $calc(10); // 30

Conclusion

Arrow functions are a concise form of closures, made for clean, short expressions in straightforward logic.

If your code has function ($x) use ($y) { return …; } — just replace it with fn() and feel the difference.

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First published in Ukrainian in the Telegram channel “Created to die” on October 17, 2025.